Overload-circuit-breaking apparatus



E. O. SCHWEITZER. OVERLOAD CIRCUIT BREAK ING APPARATUS.

APPLICATION FILED JAN. 10, i9l9 Patented. May 25, 192% 3 SHILETS-SHEET 20 SW A 2 3 v m v 1 Il I'llll'lllll Ill .iiniiiiiiiiusiiiii..iiiia ai352i??? -E. O. SCHWEITZER.

OVERLOAD CIRCUIT BREAKI NG APPARATUS.

APPLICATION FILED JAN. 10. 1919.

went e6 May 25, 192$ 3 SHEETSSHEET 3.

UNITED/STATES PATENT oF IcE.

EDMUND O. SCHWEITZER, OF CHICAGO, ILLINOIS.

OVERLOAD-CIRCUIT-BREAKING APPARATUS.

Specification of Letters Patent.

Patented May 25, 1975i).

Application filed January 10, 1919, Serial No. 270,488.

tomeans for interrupting current flow at high tension.

The object of my invention is to provide a novel method of and means forswitching and particularly for interrupting the flow of high tensioncurrent with simple and inexpensive apparatus. Other and subsidiary objeets will be apparent from the following specification.

The switching or interrupting of current flow on circuits operating onhigh tension.

is in general a difficult and dangerous matter. When a line bears aheavy flow of current at a high voltage, physical separation of theconductors is followed by an are which tends to persist to adegreedepending upon'the resistance and inductance of the circuit, thecapacity of the generating systern back of it, and the voltage on theconductors.

In practice previous to my invention, the only feasible way to switchsuch current flow was by oil switches, but oil switches are veryexpensive in cost and upkeep and in large sizes are slow to operate. Theuse of an break switches for such service has been wholly unpracticableheretofore. The reason for this is that the are which is formed destroys the switch contact. Particularly upon a shorted or overloaded linean air break switch is useless because when the blade is opened, the arcfollpws thefull movement of the blade and continues even after theswitch is fully opened. The result is the prompt destruction of theswitch. This isreadily understood whenit is considered that on ashort-circuitedline substantially is concentrated upon the production ofheat, andas the break at the switch constitutes the major part of theresistance of the circuit, an enormous amount of heat may be liberatedat the switch.

The provision of oil switches. at various .points on a line or systemwhere it is de- .sirable to have means for opening the cii=- the entirecapacity of the system cuit, is not feasible, because of first cost andfurther because of the inability to give them proper attention formaintenance. As

a result, most lines are inadequately provided with circuit breakers.

The statements above made with respect to an air break switch also holdstrue of any type of switch, the voltage interrupting capacity of whichis below that of the circuit upon which it is to be used, whether of a1rbreak switch, oil switches or any OthGPtYPB.

According to my invention I provide a switch which, of itself, isincapable of satisfactorily interrupting the flow of current/ at thevoltage at which the line is operated and by means of a fuse of specialcharacter in shunt with the switch I am able to take from the'switch theactual duty of interrupting the current fiow and place it upon I thefuse, which fuse is of such character and construction as to be capableof interrupting the flow of current at the voltage to which the line issubjected.

In the preferred form of my invention 1-80v employ an air break switchof relatively inexpensive construction and ofa'voltage interruptingcapacity lower than that required to break a heavy flow of current onthe line,

and place inshunt of this switch a fusible 35 circuit break ng device ofhigh voltage interrupting capacity but of small current carryingcapacity. The fusible circuit breaking *device which I employ ispreferably of the type shown in the patent to myself and Mr. Conrad, No.1,135,548,altl 1ough any fuse of similar characteristics and ability topositively interrupt the circuit may be employed instead. This type offuse is particularly valuable becauseof being surrounded by liquid. Itis capable of carrying a large overload current for a very short periodof time without fusing, thus permitting the switch to open far enough toprevent reformation of theharc at the contact '100 of the switch, andalso because of the ability to positively interrupt the flow of currentat this fuse.

The fuse may be connected normally in circuit in shunt with the switch,or. it may be connected in a shunt which is closed only when the switchopens with a certain time lag intervening. In the latter constructionthe fuse will be kept out of the normal flow of current and will berelatively cold so that will not blow immediately, but will per- 'mitthe switch to move to open position so J that after blowingof the fuse,the voltage of the line will not be able to reestablish the arc.

In this particular embodiment, the fuse terrupting the are at the fuseby interposition of a dieletric .medium of great strength.

In the accompanying drawings:

Figure l is a diagrammatic view of high tension three phase power orlighting circuit provided with over-load circuit breaking apparatusembodying my invention;

Figs. 2 and 3 are views of the preferred and modified form of myapparatus, respectively Fig. 4 is a longitudinal section of the fuse innormal condition, which fuse is employed by my invention;

Fig. 5 is a similar view of the fuse in operation;

Figs. 6, 7 and 8 are transverse sections taken on corresponding sectionsindicated in Fig. at; I

Fig. 9 is a front elevation of a modified form of switch embodying myinvention:

Fig. 10 is a side elevation of the same; and I Fig. 11 is a fragmentaryplanview of the same.

In the drawings I have shown the line conductors 1, 2 and. 3,representing the three high tension lines or conductors of a threephasesystem supplied by dynamo or gen e'ators l. The conductors 5, (l and Tare other line com'luctors leading off from the conductors l. 2 and 3.the conductors 5. (S and 7 being understood to run through some suitabletransmission device or other apparatus requiring overload currentprotection. Each of the lines 5. (3 and T lshow equipped with automaticoverload circuit breaking apparatus involving my present invention. Ishow in connection with line or conductor 5,

for example. the fuse S which of very low carrying capacity. preferablya very small percent. for IHSUUKQOIIO percent, of the entire carryingcapacity or load carried by I conductor 5.

I also show a circuit breaker 9 which may be any suitable or desirabletype of automatic commercial circuit breaker preferably of the airbreak'type. The contacts 1()10 of thiscircuit breaker are connected bywires ll and 12 with the line 5 so that the fuse S is in shunt of thecircuit breaker. The operating solenoid 14; of the circuit hr aker isconi ected in series with the line conductor 5 this solenoid 1 f actingupon tripping mechanism 15 to operate the circuit bro: ker when apredetermined overload traverses the conductor 5. Thus it will be seenthat when-- ever a predetermined or sullicient overload passes in theline 5 the solenoid ill will actuate the circuit breaker 9 and therebyopen line 5. It will be seen that reliability, certainty and quicknessof action are secured. the circuit breaker operating quickly when apredetermined overload is reached and then the fuse operating. Thus;with a low voltage circuit breaker of small and cheap design and a lowcapacity fuse of high voltage, a very rapid operating mechanism is olbtained with reliability of action and low maintenance cost. it will beseen atthe same time that the arcing effect is taken care of by thecharacter of the arrangement oli circuit breaker and fuse, andprotection for the translating apparatus on the line is thereby insuredfor the circuit breaker with its tripping coil in the primary circuit ismore responsive and will. operate more. quickly than the usual oilswitch and tripping mechanism at the generating stations. This permitsthe circuit breaker out at the consumeus premises to open the linebefore. the main oil circuit breakers at the central station aretripped. llettcr operating of the entire system is thereby secured.

ll hen desired. the circuit breaker may be immersed in oil. although asagencral rule this is not necessary because there is no little are. Withthe arrangement as shown in my invention, it is easy and inexpensive toreplace the fuse since it is contained in a removable cartridge as willbe explained later.

in Fig. 9 l have shown the preferred form of'apparatus which employ.'lhis enibodies a swinging knife blade switch l1") piw oted at IT to apost 18 secured to an upright support if). The blade ll) has anextension 20 to which is secured a spring '31. also fastened to thesupport 19. said spring tending todraw said extension 20 toward thesupport 19. 'l l s upright support is made of insulation. Spring contactjaws are also mounted upon the upright support; If) and are arranged tocooperate with the blade i and other contact jaws 2 1 also inounl'ed onthe support 19 are arral'iged to cooperate with the extension 20. Thesecontacts are suitably insulated from each other. An elccpivotallyconnected at its lower end to a support 26 and at its upper endconstituting a support for the links 27 and. 28 whichare pivotallyconnected to one another, by fric- I tionally engaging the under sidesof the links at their pivotal point to retain the links in the positiondisclosed in Fig. 2, it being understood that the-link 27 is in the formof a hook or catch to engage the end of the switch blade 16. A spring 29acts upon the catch 27 tending tohold the same in engage mentwith theswitch blade16. Thus, the

bladej1 6 is normally. held closed in the contact 22 by the catch 27 butwhen the solenoid 24 is actuated and the armature 25 attracted the catch27 being shifted due to the action of the spring member 29 so as todisengage the blade 16, thereby permitting the spring 21 to. actuate.the same and separate the blade 16 from the contact 22 and causeextensions 20 to connect withthe contact jaws 23, the

' links 27 and 28v having a loose connection with one another and withthe. armature 25 with sufficient loose motion to permit a slightbuckling of the links 27 and 28 so as to cause a'r'elease or trip of theblade 16.

On the eother side of the upright 19 are mounted a pair of posts BOand31 which support-an inclosed fuse 32, the construction of which is shownin-Figs. 4 to 8 and will be described later. The arrangement is soconnected that; the solenoid 24 is included in the circuit as shown inFig. 1, and when and the connection of the fuse in shunt. llnthesolenoid is energized by an overload current and the blade 16 released,the circuit through the blade 16 by way of contact jaws 22 is opened andthefuse 32 is connectedin shunt by: the extension 20 meeting the springjaws 23, the connection to-the swinging blade 16'. and extension 20being by way of metal rods to posts 18.

- In this embod ment of the invention, the

fuse 32 is not normally in circuit, and hence is not sub ect to beingheated by current flowing during 'normal operation. A furtheradvantage'of this form lies in the lag between the opening movement ofthe switch less the resistance and circuit carrying capacity of the fuseare carefully proportioned to coiiperate with the voltage and openingaction of the fuse, there is a tendency when the fuse is permanently inshunt for the fuse to blow before the switch is far enough opened toprevent the arc being re-formed at the switch.

overcomes this tendency to blow immediately, to a noticeable extent andis an important feature of the invention. ln the preferred form of'Fig.2 the switch gets an In the form of apparatus which I employ the liquidsubmerged fusematerial 40 having brass ferrules 41 and 42 at top andbottom. which ferrules are cemented in place on the sleeve. A fusibleelement 43 inclosed in a cork barrier 44 is connected to. a removablevent or disk\45 by a link 46. .The vent or disk 45 is soldered on theupper ferrule and is adapted to be 7 blown off in the case of vigorousblowing of the fuse. The lower end of the fusible element 43 isconnected by a link 47 to acrossbar 48, which cross bar is mechanicallyconnected to the wooden liquid director 49. A

link 50 connects the cross-ba'rto a helical spring 51, the lower end ofwhich is connected to the lower ferrule 42. A flexible cable 52 isconnected in shunt of the spring 51 to preventoverheating anddestruction of the temper of the spring. The entire sleeve is filledwith carbon tetrachlorid or other similar suitable insulating material.\Vhen the element 43 is fused the spring draws the terminal or link 47down into the sleeve and at the same-time the liquid is projected in astream by the liquid director 49, asshown inFig. 5, thus positivelyinterrupting the flow of current. The fusible .element 43 is made of asmall percent. of the carrying capacity of the main switch to which itis connected in shunt. The resistance is also preferably madesufficiently high so that if the element is normally connected in shuntof the switch, the flow of current through it will be small enough notto blow the fuse under all conditions of current flow to which it issubjected when the switch blade is still closed. The submergence of thefuse also gives it a greater heatabsorbing ability so that actualblowing is,

delayed until the movable blade has had an opportunity to leave thestationary contact. This is highly beneficial in that it permits theswitch to move farther toward the open position and thus get farther outof range of the fixed contact before the fuse actually blows. After thefuse once blows the are which is caused by such blowing. is cX-'.tinguished almost instantaneously.

Operation of the complete device. shown in Fig. 3 and diagrammaticallyindicated in reached a predetermined.position the rear end of the bladeconnects with the fuse 32 in shunt of the break at the switch contactand the current how is established through the fuse. The fuse then blowsand positively stops the flow of current by interposing the arcextinguishing liquid which is a medium of high dielectric strengthbetween the separated terminals of the fuse:

The fuse and switch are scpa ated by in sulating barriers consisting ofthe insulating support 19 and also the sleeve 40 to prevent mutualinteraction between the fusible element and the switch, and particularlyto prevent the are at the fuse from reestabhshi the are through theswitch.

In l 3 I have shown an arrangement very similar to that of Fig. 2, butinstead having three posts on the upright 19 have shown in Fig. 3 onlytwo posts, namely the spring jaws E22 and the post 18 to which theswitch blade 16 is pivoted. The fuse is connected with the posts 30, asin Fig. 2 and also with the posts 31, being a rear extension of the post1 Thus a fuse 32 is normally connected in shunt with the circuit breakeror switch instead of being thrown higs. 9 and 10 I have illustrated amodiacation of my invention suitable for use in connection with certainwell known indoor disconnecting switches. The switch shown comprises theupper terminal 60 and the lower terminal (31, consisting of a metal headhaving a screw threaded shank adapted to be secured in a suitablepartition or mountin as is customary indoor inclosed switches of thischaracter. The hear. has a plurality of fins or plates (36 securedthereto, these plates forming the hinge for the movable blade members67, which in this case are shown as three in number. The up per block 6%has a plurality of similar fins or plates 68 secured thereto for makingcontact with the free ends of the switch blades A hinge pin or bolt ispassed through the hinge plates 66 and through the lower ends of theblades G7 to form the pivots for the mo 'able blades. The movable blades.are thus gripped between pairs of the hinge plates and held in placeyieldingly by means of the spring washers and the bolts 69.

The blades are provided with a suitable eye or other engaging portion bywhich the switch may be manually opened or closed. I connect the fuse 72in parallel with the switch. The upper ferrulefTZB of the fuse 72 ismounted in a suitable contact clipi i which in turn is supported from abar of insulation 75 which holds the upper contact clip i i andconnected parts at a suitable distance and in suitable alinement withrespect to the lower contact clip 76. The lower contact clip 76 whichengages the fuse ferrule 7T mounted upon a suitable bracket '78 i whichconnects electrically with the pivot plate 66 through the bent or U-shaped connecting member 79, which has its outer end bolted to the bracket78 by means of the bolt 80. The inner end of the U-shaped member if) isfastened under the adjacent spring washer and is pivoted upon the bolt(39. ii similar ii-shaped member 81 is connected at the upper end of thebar of insulation and the clip iiis connected to said U-shaped member 81by thedn'acket and the bolt b3. The inner end of the U-shaped member 81forms a movable switch contact element which engages between theoutermost plate or iin (S8 and an added plate or lin 81 which is boltedto the side of the block (it. A suitable eye is bolted to the U-shapedmember 81 by the bolt 86 so that the insulating bar I?) with itsattached part may be swung about the pivot pin (3!).

The fuse T2 is of the type and character illustrated in the previousfigures. mounted on a swinging blade of insulation 72 so that the upperend of the mounting may be disconnected from the upper terminal (30which preferably is the live. terminal so that the fuse may be withdrawnand replaced without'incurring the danger of contact with live parts.

The operation of follows: smiling and th a s the fuse is this form ofdevice is as that the switch is closed plished by inserting a hook inthe hole in the eye Tl and pulling the switch blades 67 outwardly intothe position shown in Fig. 10. The 'i'urrent is diverted to the fuse T2and for an appreciable period of time the current shunted through saidfuse so that very little arc occurs at the separation of the blades 67from thecontact (5S, and after the blades have been moved outward farenough so that the voltage will not reestablish the arc the fuse 72blows, positively interrupting the connection between the switchterminals. The operating hook may then be inserted in the eye 35 todisconnect the terminals of the fuse so that the fuse may be withdrawnand replaced with a. fuse in the set condition.

it will be apparent from the above description and from the drawingsthat this form of construction permits the addition of certain parts tostandard switches so that my invention may be applied to switchesalready in use.

it will beunderstood that changes and modifications may be made withoutdeparting from the spirit of the invention.

What I claim is:

l. The method of interrupting a How of current in a conductorwhichcomprises mechanically breaking the conductor, conducting thecurrent flow wholly through a fusibleelement independent of the break,fusing it is connected. in place, inter- .ruption of the flow of currentis accomflow of current at said fusible element by inter-posing a fluiddielectric of greater strength than that prevailing at the mechanicalbreak.

2. The method of interrupting the flow; of current in a conductor whichcomprises Inechanically breaking the conductor, conducting the currentflow wholly through a fusible element independent of the break, fusingthe tusibleiclement a short interval of time after the opening of theswitch, and promptly interrupting the flow of current at said fusibleelement by interposing a dielectric of greater strength than thatprevailing at the mechanical break.

3. The method of interrupting the tlow of current in a conductor whichcomprises mechanically breaking the conductor, conducting the currentflow wholly through a fusible elementindependent of the break, coolingthe fusible element with a liquid dielectric to delay theoperation otthe same, then tusing the fusible element and interrupting the flow(if-current at said "fusible element by inter-posing said liquiddielectric.

4. In combination, [ill'fiil' break switch having means for opening thesame, a fusile element, means for connecting the fusible element acrossI the terminals of the s itch when the switch is opened, a barrier ofinsulation between the fusible element and the switch to preventmutualinteraction between the fusible element and the switch, and meansfor interposing'a dielectric medium of greater strength than air betweenthe terminals of the fuse after the same closes.

in a device for interrupting current flow at high voltage, a-switch ofless interrupting capacity than that required to break the flow ofcurrent at said voltage, a fusible element and means for connecting thefusible element across the terminals of the switch, said fusible elementbeing submerged in a liquid of relatively great dielectric strength topermit a. slight delay in the l'using of the element and to positivelyextinguish the are at the fuse. I

6. ln combination, an break switch, a fusible element connected in shuntof the air break switch, and a liquid dielectric surrounding the fusibleelement for initially cooling the same when the switch is opened and toextinguish the are when the fusible element is fused.

7. in a device for inte flow at high voltage, a sw c h inherently unableto break the full load flow of current the desired voltage, nsible ele'ient in shunt of the switch, sait ing or a current condr I a smallpercentage of 11A; of the current carrying capacityei the switch andbeing ipting a current of a voltage interrupting capacity in excess ofthe voltage impressed upon the switch and a liquid for. cooling the fuseto permit a slight delay in the operation of the same. ,8. Incombination, a switch, a fuse and means for connecting the fuse acrossthe terminals of the switch, said fuse having means to delay the blowingof the same until after the switch is opened a substantial distance. p

9. ln combination, a pair of stationary terminals, a switch bladepivoted on one of the terminals, the other of said terminals havingcontacts for engaging the switch blade, a pair of terminal clips, a fusemounted in said clips, a non-conducting member connecting said clips andmeans for connecting the clips to said terminals.

10. In combination, a pair of stationaryterminals, a switch bladepivoted on one of the terminals, the other of said terminals havlngcontacts tor engaging the switch blade, a pair of terminal clips, afusemounted in said clips, a non-conducting member connecting saidclips, a pair of connecting members for connecting said clips to saidterminals, one of said members being pivoted on one of said terminalsand the other of said connecting members being adapted to engage anddisengage electrically the other terminal.

l ain combination, a pair of terminals, a switch blade mounted on one ofsaid terminals, a contact mounted on the other terminal, a bar ctinsulation pivotally mounted on the same axis as the switch blade,:t'use mounted on said bar or insulation and means for connectingthefuse in parallel with the switch,

12. in combination, a pairot terminals, a switch blade mounted on one ofsaid termials. a contact on the other terminal for engaging the switchblade, a first member nected said ruse clips and adapted to be con e edin parallel with the switch across said combf ration, a pair 0" .r

' ivot" on one "\rnnna time iectcd to s adapted to e con-act jaws on ore other 1 ar tact L cans being connected {0 e 'ininal the fuse.

. In c nibinaticn. a pair 0" v i pivot" 'f aninal ha-.'ing contactpivotally mounted on the one terminal llllt having means for engagingthe contact jaws on the other terminal to place the fuse in parallelwith the switch.

15. In combination, a pair of terminals a switch blade pivotally mountedon one 01 said terminals, a fuse also pivotally mounted on-sairl. oneterminal, eontaet jaws on the other terminal, a eontaet member on thefuse for engaging said contact jaws and for placing the fuse in parallelwith the switch. In witness whereof .l hereunto suhseriho my name this7th (lay of January, 19M).

EDMUND SUllll llll'lZllR.

